Manipulators, in particular robots in industrial applications, are frequently used in a highly alternating mode. In order to execute the same tasks repeatedly successively as quickly as possible, the manipulator typically drives to a programmed track point at the maximal possible acceleration and brakes promptly before said track point with the maximal possible deceleration in order to accommodate the prescribed velocity, in particular in order to stop at said point. Subsequently, the next track point is again approached at the maximal possible acceleration, and so on. Examples of this are welding, painting and commissioning tasks, which are automatically processed by industrial robots.
During the acceleration phases, the manipulators accumulate kinetic energy. During the deceleration phases, said kinetic energy is converted to electrical energy by the drives of the manipulators and subsequently dissipated as heat via brake choppers in ballast resistors, such that the intermediate circuit voltage does not exceed the maximal permissible voltages of the manipulators. Depending on the application, this loss of energy also applies to the converted potential energy.
This loss of energy to the environment, in particular through the heat dissipated in the brake resistors, is contingent on a high degree of energy input during the operation of the manipulator(s) and represents a substantial impairment to the efficiency of current manipulator configurations.
A typical measure for reducing the energy requirements is the counterbalancing of industrial robots, as is, in particular, proposed in EP 0 914 911 B1. A counterbalancing of this type causes a reduction in the differences in the potential energies at different robot poses, such that preferably in the base axis of the robot, weaker drives and brakes are needed in order to consume less energy for the same movements.
An electrical energy storage device is known from DE 10 2009 054 818 A1, by means of which an intermediate circuit power can be stored. This energy storage device is created using a capacitor. A substantial disadvantage of a storage device of this type is the limited storage capacity, which only represents a fraction of the energy that is consumed by a robot for each movement.
An electrical energy recovery of excess energy from an intermediate circuit to an energy network is known from DE 10 2008 019 294 A1. Disadvantages of this method consist, in particular, of the additional costs for the transformation equipment for converting direct current to alternating current, and the additional energy losses resulting thereby, in particular in the rectifiers and in the commutation inductances.